It was near impossible for it to jam or break when no enemies were around.
Well, why would you be firing the gun if no enemies were around?
They do jam with no enemies around though. Each weapon I bought I would go out and fire until it jammed to get a measure of how long I could use it.
they do actually search for your general area when they see a bullet fly past them instead of just running around like chickens.
In FC2, at the first hint of a sniper, they would all take cover. They would then move from cover to cover while approaching your suspected position. They just didn't all turn and rush like they do now. Someone's sniping, so you're going to charge them? Great way to get your head shot off, and many times that's exactly what I do to them.
Far Cry 2 wasn't harder really. Some annoyances just made it less convenient. The malaria thing was just a pain, the degrading weapons never really came into play for me except in multiplayer where they'd try to end my kill streaks, and the instant respawn was just dumb.
The stealth was kinda busted too. Not that its much better in this.
Far Cry 2 did definitely have vastly superior destruction and physics when grendades blew up inbetween a bunch of bushes and you could destroy pretty much all the vegetation. I also thought the fire looked better when spreading.
As for the games themselves, I'd say I like Far Cry 3 more. Much better story, far less repeptitive missionns, better driving, better gun play, better weapons/customization, takedowns etc.
Don't get me wrong, I badly miss weapon jamming. Not so much degradation, because it was far too extreme, but some of the best and most intense moments in FC2 came when my weapons jammed. I thought it was awesome that a game had incorporated that since almost none do. Weapons do jam. Period.
I do miss that enemies would help eachother out and carry them if they were injured, but I would not go as far as to say the AI was better.
Overall, I think if you combine elements of both games you get the best Far Cry you can possibly make.